DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Specification
The disclosure is objected to because of the following informalities:
In paragraph [0021] of the disclosure as amended, please change “herein "microns" or "urn" refer to [quote marks reproduced from specification]” to “herein "microns" or "µm" refer to”.
In paragraph [0043] of the specification as amended, please change “distribution of 20-63um” to “distribution of 20-63 µm”.
Appropriate correction is required.
Claim Objections
Claim 16 objected to because of the following informalities:
In claim 16, please change “of the densification is” to “of the densification aid is”.
Appropriate correction is required.
Claim Rejections - 35 USC § 112
The following is a quotation of 35 U.S.C. 112(b):
(b) CONCLUSION.—The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention.
The following is a quotation of 35 U.S.C. 112 (pre-AIA ), second paragraph:
The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention.
Claims 15 and 17-21 are rejected under 35 U.S.C. 112(b) or 35 U.S.C. 112 (pre-AIA ), second paragraph, as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor (or for applications subject to pre-AIA 35 U.S.C. 112, the applicant), regards as the invention.
The term “substantially reside in interstitial spaces of the aluminum alloy powder” in claims 15 and 17is a relative term which renders the claim indefinite. The term “substantially reside” is not defined by the claim, the specification does not provide a standard for ascertaining the requisite degree, and one of ordinary skill in the art would not be reasonably apprised of the scope of the invention. The present disclosure states “[u]nless otherwise stated, the words “about” and “substantially” as used herein are to be construed as meaning the normal measuring and/or fabrication limitations related to the value or condition which the word “about” or “substantially” modifies” (paragraph [0016] of the disclosure as amended). The term “substantially reside” is not a numerical quantity, and the present disclosure does not provide some metric or threshold of encapsulation the densification aid must meet in order to be considered to “substantially reside” in interstitials. Further, considering both claim 15 and claim 17 claim a densification aid ranging from 0.1 to about 3.0 weight % of the build powder, the majority of the build powder is the aluminum alloy powder; therefore, the densification aid will be completely surrounded by aluminum alloy powder regardless of the particle size of the densification aid. While a relatively large densification aid particle may be less effective as a densification aid, that particle would still necessarily occupy volume which is not occupied by the aluminum alloy particles, and therefore reside in interstitial spaces of the aluminum alloy particles.
Claims 18-21 are rejected under 35 USC 112(b) because they depend on claim 17.
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention.
Claim(s) 1-7 and 9-14 is/are rejected under 35 U.S.C. 103 as being unpatentable over Liu (US7517492) in view of Myers (Myers, Neal, and Randall German. "Rapid Prototyping of Aluminum by Selective Laser Sintering." Metal Powder Deposition for Rapid Manufacturing: Proceedings of the 2002 International Conference on Metal Powder Deposition for Rapid Manufacturing. Metal Powder Industries Federation, 2002) and Xiao (CN110405214A). Liu is cited in the IDS filed July 4, 2023. References to Xiao are directed to the examiner-supplied English language translation.
Regarding claim 1, Liu discloses a method for producing a densified aluminum part (sintered aluminum article column 1 lines 17-20, column 3 lines 20-22). Liu discloses forming a green part (3DP process printed article) from build powder and a binder (column 6 lines 35-53). Liu discloses that the build powder comprises aluminum alloy powder comprising aluminum alloy particles (column 3 lines 54-58). Liu exemplifies aluminum alloy 6061 (column 4 lines 46-60, column 9 lines 18-19, 39-40, 62-63, column 10 lines 7-8), which Liu discloses has an aluminum alloy composition comprising a magnesium content of 0.89 wt% of the aluminum alloy composition (column 9 lines 19-22). A magnesium content of 0.89 weight% lies within the claimed range from about 0.5 to about 5 weight%. Liu discloses that the build powder comprises a densification aid (sintering aid) mixed with the aluminum alloy powder (column 6 lines 6-11, column 7 lines 60-63, claim 6).
Liu discloses densifying the green part by heating the green part under nitrogen gas (column 6 lines 58-63, column 7 lines 15-38). Liu discloses that the sintering is supersolidus liquid phase sintering, or, as when a sintering aid is used, liquid phase sintering (column 7 lines 19-21). As supersolidus sintering (as opposed to complete melting) is a sintering which by definition occurs between solidus and liquid temperature of the sintered material, Liu discloses that the densifying comprises heating to a sintering temperature between the solidus and liquid temperature of the aluminum alloy. Liu further discloses that sintering with a sintering aid promotes reaction-assisted (attacks the alumina film) super-solidus liquid phase sintering (column 1 line 64 to column 2 line 13). Liu discloses that the densified aluminum part (sintered article) has a relative density of at least about 60%; more preferably, a relative density of at least about 75%; even more preferably, a relative density of at least about 85%; and most preferably a relative density of at least about 95% (column 6 lines 30-35). Liu discloses that the parameters can be adjusted to arrive at a desired relative density (column 6 lines 23-30). The most preferred range of at least about 95% discloses by Liu (column 6 lines 23-30) directly meets the density range of at least 95%, and the broader ranges of relative densities disclosed by Liu (column 6 lines 30-35) overlap a range of at least 95%. When claimed ranges overlap or lie inside ranges disclosed by the prior art a prima facie case of obviousness exists. See MPEP 2144.05(I).
Liu is silent on the amount and relative sizes of the densification (sintering) aid, but Liu explicitly directs readers to the Myers reference regarding background knowledge of powder mixtures comprising aluminum and a sintering aid (column 1 line 64 to column 2 line 11).
Myers teaches producing a densified aluminum part (aluminum powder material) (abstract, page 235 Experimental Procedure section). Myers teaches forming a green part from build powder and a binder (Table V, abstract, page 235 Experimental Procedure Section). Myers forms green test slugs comprising 2% by weight binder (page 235 Experimental Procedure Section, page 238 Results and Discussion section, Table III), and forms example green parts with 4% by weight binder (page 235 Experimental Procedure Section, Page 239 Results and Discussion section Table V). Myers teaches that the build powder comprises aluminum alloy powder comprising aluminum alloy particles and having an aluminum alloy composition of alloy 6061 aluminum (“-170 mesh 6061” Table I, page 235 Experimental Procedure). Myers teaches that the build powder comprises a densification aid mixed with the aluminum alloy powder (tin (Sn) and/or magnesium (Mg) Abstract, Table II, abstract on page 232 and Background section on page 233 establish Sn and Mg as sintering aids). Myers teaches examples comprising 2% by weight Mg mixed with 6061 alloy and a combination of 2% Mg and 1% Sn by weight% mixed with 6061 alloy (Tables II, IV, page 238 Results and Discussion section), thereby teaching amounts of 2% and 3% densification(sintering) of the build powder. Myers teaches Mg powder particles have an average particle size (D50) of 41.6 microns; Sn powder particles have an average particle size (D50) of 10.6 microns, and 6061 alloy particles have an average particle size (D50) of 42.3 microns (Table I). Myers teaches densifying the green part by heating the green part under a continuous flow of nitrogen gas (flowing nitrogen gas, abstract) (page 235 Experimental Procedure section, page 239 Results and Discussion section). Myers teaches that sintering aluminum material with a sintering aid causes reaction-assisted liquid-phase sintering (page 233 Background section). Myers teaches that the sintered aluminum part has nearly full density (Table III, page 236 Results and Discussion section, page 241 Summary).
Both Liu and Myers teach similar processes for producing sintered 6061 alloy parts comprising a sintering aid.
In order to perform the embodiment comprising a densification (sintering) aid disclosed by Liu, applied above, it would have been necessary for one of ordinary skill in the art, at the time of filing, to supply the densification powder particles in some proportion and some particle size. Considering Liu explicitly cites Myers for sintering with a sintering aid (column 1 line 64 to column 2 line 11) in determining sintering aid parameters for the process disclosed by Liu, it would have been obvious for one of ordinary skill in the art at the time of filing to select sintering aid proportions of 2-3% and particle sizes which Myers teaches as effective for sintering aids for 6061 aluminum alloys (Tables I-II, page 238 Results and Discussion section), thereby predictably proportioning feed material in the process disclosed by Liu in amounts suitable for liquid phase sintering taught by both Liu (column 7 lines 15-38) and Myers (page 233). Both the significantly smaller Sn powder size and the slightly smaller Mg particle size relative to the alloy powder taught by Myers (Table I) meet the relative particle size limitation recited in claim 1.
Liu discloses that the green article has about 10% by volume binder (column 6 lines 46-50). Liu does not teach weight percentages of the binder, and Liu does not teach results of varying binder amounts. Liu further does not exemplify embodiments comprising binder. Myers teaches embodiments wherein green article comprises 2% by weight and embodiments wherein the green article comprises 4% by weight (page 235 Experimental Procedure Section, pages 238-239 Results and Discussion section, Tables III, V). Myers teaches that the amount of binder in the manufactured part affects the performance of the part (page 238). Considering Liu does not disclose results, reasons, or specific examples for setting a binder to the disclosed volume fraction, whereas Myers teaches and exemplifies specific binder proportions and teaches that the binder proportions affect results (page 238), in order to ensure effective performance of the formed part, it would have been obvious to one of ordinary skill in the art at the time of filing to form the green part with 2% or 4% by weight binder, which Myers teaches as effective for producing such sintered aluminum parts (pages 235-236, 238), and which Myers teaches affects the performance of the formed part (page 238), thereby predictably forming a part with desired density and mechanical properties (pages 236, 238-239, Tables III, IV). 2% and 4% by weight are both within the claimed range of less than 5% by weight binder.
Liu discloses that where a binder has been used in forming the aluminum powder into a shape, the heating cycle is controlled to permit the binder to be removed (column 7 lines 31-33), and Myers teaches that gas flow can affect part distortion (page 241 Summary section). Liu in view of Myers does not disclose that the heating the green part (printed article) under nitrogen gas, applied above, comprises heating the green part under a continuous flow of nitrogen gas of at least 5 standard cubic feet per hour (SCFH).
Xiao teaches a method for producing a densified part (claim 1, [0001], [0019]). Xiao teaches forming a green part (billet) from build powder and a binder [0012], [0043], [0068]. Xiao teaches that the build powder comprises an alloy powder comprising alloy particles (stainless steel powder, as opposed to particles of constituent elements) [0044]. Xiao teaches densifying the green part by heating the green part under a continuous flow of nitrogen gas [0015-17], [0023-25], [0049-59]. Xiao teaches supplying the nitrogen flow at rates of 20L/min to 45L/min at stages of the sintering [0052-53]. Xiao teaches that the flow of nitrogen maintains the nitrogen equilibrium allowing nitrogen to enter pores [0052-53], which Xiao teaches allows more densely sintering as sintering temperature rises [0054]. Xiao further teaches heating for binder removal under a flow of nitrogen gas of 10-100 L/min (claim 6, [0025]).
Both Xiao and Liu in view of Myers, applied above teach producing a part by forming a green part from build material comprising binder and alloy powder particles and sintering under nitrogen gas.
It would have been obvious for one of ordinary skill in the art at the time of filing to provide the nitrogen in the method disclosed by Liu in view of Myers, applied above, at a continuous flow rate of 20-45 L/min because Xiao teaches that providing nitrogen in a sintering step at 20-45 L/min allows more densely sintering as sintering temperature rises [0054]. Further, considering Xiao teaches that a nitrogen flow of 10-100 L/min as suitable conditions for binder removal (claim 6, [0025]), a range of 20-45 L/min would predictably facilitate residual binder removal, which Liu discloses controlling in the heating step (column 7 lines 31-33). 20-45 L/min is equivalent to 42.4-95.3 cubic feet per hour, which meets a range of at least 5 SCFH.
Regarding claims 2 and 3, Liu exemplifies aluminum alloy 6061 (column 4 lines 46-60, column 9 lines 18-19, 39-40, 62-63, column 10 lines 7-8), which is a 6XXX series alloy and an aluminum alloy which is a 6061 alloy, thereby meeting the additional limitations recited in both claim 2 and claim 3.
Regarding claim 4, Liu discloses that the aluminum alloy powder has a particle size in the range from about 1 micron to about 500 microns, and preferably a range from about 45 microns to about 106 microns (column 5 lines 49-55). Liu discloses reasons for why particles which are too coarse or too fine should not be used (column 5 lines 49-55). A range of about 1 micron to about 500 microns encompasses the range recited in claim 4, and a range from about 45 microns to about 106 microns overlaps the range recited in claim 4. When claimed ranges overlap or lie inside ranges disclosed by the prior art a prima facie case of obviousness exists. See MPEP 2144.05(I).
Regarding claims 5 and 6, Liu discloses that the densification (sintering) aid is selected from the group consisting of tin and magnesium (column 6 lines 6-11, claim 7). Tin or magnesium meet the additional limitations recited in claim 5, and tin meets the additional limitations recited in claim 6.
Regarding claim 7, Liu discloses that the sintering temperature between about 550
°
C to 650
°
C (column 7 lines 21-23), which overlaps a range from about 610 C to about 660 C. When claimed ranges overlap or lie inside ranges disclosed by the prior art a prima facie case of obviousness exists. See MPEP 2144.05(I).
Regarding claim 9, the nitrogen flow range of 42.4-95.3 cubic feet per hour taught by Xiao [0052-54] overlaps a range of about 5 SCFH to about [emphasis added] 40 SCFH in view of paragraph [0016] of the present disclosure. When claimed ranges overlap or lie inside ranges disclosed by the prior art a prima facie case of obviousness exists. See MPEP 2144.05(I). Further, the 10-100 L/min nitrogen flow, which Xiao teaches as effective for binder removal ([0025], claim 6) is equivalent to 21.2-212 cubic feet per hour, and considering Liu teaches controlling heating conditions to remove binder (column 7 lines 31-33), in view of Xiao’s teachings of the effectiveness of 10-100 L/min for binder removal, a nitrogen flow rate of 10-100 L/min in a step wherein binder is removed, would have been obvious to one of ordinary skill in the art at the time of filing.
Regarding claim 10, Liu discloses an embodiment wherein the forming step is performed by binder jet additive manufacturing (3DP Process column 6 lines 35-63).
Regarding claim 11, Liu and Myers exemplify 60610 aluminum alloy (Liu column 4 lines 46-60, column 9 lines 18-19, 39-40, 62-63, column 10 lines 7-8; Myers Table I). Liu discloses tin (Sn) as a densification (sintering) aid (column 6 lines 6-11, claim 7), and the densification (sintering) aid proportion taught by Myers, applied above, comprises tin (Sn) in 1% (Table II). The 42.4-95.3 cubic feet per hour nitrogen flow taught by Xiao [0052-54], applied in the process disclosed by Liu in view of Myers and Xiao applied above is at least 20 SCFH.
Regarding claims 12 and 13, Liu discloses that the densified aluminum part (sintered article) has a relative density of at least about 60%; more preferably, a relative density of at least about 75%; even more preferably, a relative density of at least about 85%; and most preferably a relative density of at least about 95% (column 6 lines 30-35). Liu discloses that the parameters can be adjusted to arrive at a desired relative density (column 6 lines 23-30). The ranges of relative densities disclosed by Liu (column 6 lines 30-35) overlap a range of at least 97%, as recited in present claim 12 and a range of at least 99%, as recited in present claim 13. When claimed ranges overlap or lie inside ranges disclosed by the prior art a prima facie case of obviousness exists. See MPEP 2144.05(I).
Regarding claim 14, Liu discloses that forming the green part results in 30-60% of the volume of the green part of powder (printed article) (column 6 lines 47-49). As relative green density of a porous article is the volume percentage of the article which is not void space, the 30-60% volume disclosed by Liu (column 6 lines 47-49) overlaps a range of densities of a green part of about 50% to about 65%. When claimed ranges overlap or lie inside ranges disclosed by the prior art a prima facie case of obviousness exists. See MPEP 2144.05(I).
Claim(s) 15-16 is/are rejected under 35 U.S.C. 103 as being unpatentable over Liu (US7517492) in view of Myers (Myers, Neal, and Randall German. "Rapid Prototyping of Aluminum by Selective Laser Sintering." Metal Powder Deposition for Rapid Manufacturing: Proceedings of the 2002 International Conference on Metal Powder Deposition for Rapid Manufacturing. Metal Powder Industries Federation, 2002) and Xiao (CN110405214A) as applied to claim 1 above, and further in view of Hirata (US20160325356).
Regarding claims 15 and 16, both Liu (column 5 lines 49-55) and Myers (page 233) teach controlling overall system particle size. While the Sn particle size taught by Myers (Table I) is sufficiently smaller than the 6061 alloy particle size taught by Myers (Table I) that the Sn particles likely would reside within spaces between alloy particles, Liu in view of Myers and Xiao does not teach specifically reasons for selecting relative particle sizes.
Hirata teaches an inkjet method for forming a part [0008], [0041-0042]. Hirata teaches forming a green part (three-dimensional shaped article) from build powder (first and second inorganic particles) and a binder (binding agent) [0008], [0009], [0020], [0025], [0041-42], [0046], [0118]. Hirata teaches that the build material comprises a first inorganic material which may be particles of an aluminum alloy powder [0045-46], [0053]. Hirata teaches that build material includes second inorganic material which may be a powder of copper, tin, lead, or silver [0008-10], [0086-88]. Hirata teaches densifying the green part by heating to sinter the part [0020], [0083], [0098]. Hirata teaches that ratio between the average particle size of the first inorganic particles and the average particle size of the second inorganic particles is in a range of 50000:1 to 10:1 [0089]. Hirata teaches that in sizing according to such a range of ratios, it is possible to allow the second inorganic particles to easily enter interstitial spaces (a void) between the first inorganic particles [0089], which renders possible an increase in density of both the first and second inorganic particles in a more uniform manner [0089], which yields a three-dimensional shaped article in which the density of the inorganic particles is increased in a more uniform manner [0089].
Both Hirata and Liu in view of Myers and Xiao teach methods for producing a densified part from a build material comprising inorganic particles and a binder.
It would have been obvious for one of ordinary skill in the art to size the densification (sintering) aid in the process disclosed by Liu in view of Myers and Xiao, applied above, such that the densification (sintering) aid resides in interstitial spaces of the aluminum alloy powder because Hirata teaches that sizing second organic particles to reside in interstitial spaces of first inorganic particles, results in an increase in density and an improved density uniformity [0089], thereby further facilitating density control in the process disclosed by Liu (column 8 lines 20-32). Densification aid residing in interstitial spaces of the aluminum alloy powder meets the additional limitations of both claim 15 and claim 16.
Claim(s) 17-21 is/are rejected under 35 U.S.C. 103 as being unpatentable over Liu (US7517492) in view of Myers (Myers, Neal, and Randall German. "Rapid Prototyping of Aluminum by Selective Laser Sintering." Metal Powder Deposition for Rapid Manufacturing: Proceedings of the 2002 International Conference on Metal Powder Deposition for Rapid Manufacturing. Metal Powder Industries Federation, 2002), Xiao (CN110405214A), and Hirata (US20160325356).
Regarding claims 17 and 21, Liu discloses a method for producing a densified aluminum part (sintered aluminum article column 1 lines 17-20, column 3 lines 20-22). Liu discloses forming a green part (3DP process printed article) by binder jet additive manufacturing from build powder and a binder (column 6 lines 35-53). Liu discloses that forming the green part results in 30-60% of the volume of the green part of powder (printed article) (column 6 lines 47-49). As relative green density of a porous article is the volume percentage of the article which is not void space, the 30-60% volume disclosed by Liu (column 6 lines 47-49) overlaps a range of densities of a green part of about 50% to about 65%. When claimed ranges overlap or lie inside ranges disclosed by the prior art a prima facie case of obviousness exists. See MPEP 2144.05(I).
Liu discloses that the build powder comprises aluminum alloy powder comprising aluminum alloy particles (column 3 lines 54-58). Liu exemplifies aluminum alloy 6061 (column 4 lines 46-60, column 9 lines 18-19, 39-40, 62-63, column 10 lines 7-8), which Liu discloses has an aluminum alloy composition comprising a magnesium content of 0.89 wt% of the aluminum alloy composition (column 9 lines 19-22); therefore, Liu discloses that the build powder comprises: an aluminum 6061 alloy powder comprising aluminum 6061 alloy particles and having an aluminum alloy composition comprising a magnesium content of 0.89%. Liu discloses that the build powder comprises a densification aid (sintering aid) mixed with the aluminum alloy powder (column 6 lines 6-11, column 7 lines 60-63, claim 6). Liu discloses that the densification (sintering) aid is selected from the group consisting of tin and magnesium (column 6 lines 6-11, claim 7).
Liu discloses densifying the green part by heating the green part under nitrogen gas (column 6 lines 58-63, column 7 lines 15-38). Liu discloses that the sintering is supersolidus liquid phase sintering, or, as when a sintering aid is used, liquid phase sintering (column 7 lines 19-21). As supersolidus sintering (as opposed to complete melting) is a sintering which by definition occurs between solidus and liquid temperature of the sintered material, Liu discloses that the densifying comprises heating to a sintering temperature between the solidus and liquid temperature of the aluminum alloy. Liu further discloses that sintering with a sintering aid promotes reaction-assisted (attacks the alumina film) super-solidus liquid phase sintering (column 1 line 64 to column 2 line 13). Liu discloses that the densified aluminum part (sintered article) has a relative density of at least about 60%; more preferably, a relative density of at least about 75%; even more preferably, a relative density of at least about 85%; and most preferably a relative density of at least about 95% (column 6 lines 30-35). Liu discloses that the parameters can be adjusted to arrive at a desired relative density (column 6 lines 23-30). The most preferred range of at least about 95% discloses by Liu (column 6 lines 23-30) directly meets the density range of at least 95%, and the broader ranges of relative densities disclosed by Liu (column 6 lines 30-35) overlap a range of at least 95%. When claimed ranges overlap or lie inside ranges disclosed by the prior art a prima facie case of obviousness exists. See MPEP 2144.05(I).
Liu is silent on the amount of the densification (sintering) aid, but Liu explicitly directs readers to the Myers reference regarding background knowledge of powder mixtures comprising aluminum and a sintering aid (column 1 line 64 to column 2 line 11).
Myers teaches producing a densified aluminum part (aluminum powder material) (abstract, page 235 Experimental Procedure section). Myers teaches forming a green part from build powder and a binder (Table V, abstract, page 235 Experimental Procedure Section). Myers forms green test slugs comprising 2% by weight binder (page 235 Experimental Procedure Section, page 238 Results and Discussion section, Table III), and forms example green parts with 4% by weight binder (page 235 Experimental Procedure Section, Page 239 Results and Discussion section Table V). Myers teaches that the build powder comprises aluminum alloy powder comprising aluminum alloy particles and having an aluminum alloy composition of alloy 6061 aluminum (“-170 mesh 6061” Table I, page 235 Experimental Procedure). Myers teaches that the build powder comprises a densification aid mixed with the aluminum alloy powder (tin (Sn) and/or magnesium (Mg) Abstract, Table II, abstract on page 232 and Background section on page 233 establish Sn and Mg as sintering aids). Myers teaches examples comprising 2% by weight Mg mixed with 6061 alloy and a combination of 2% Mg and 1% Sn by weight% mixed with 6061 alloy (Tables II, IV, page 238 Results and Discussion section), thereby teaching amounts of 2% and 3% densification(sintering) of the build powder. Myers teaches densifying the green part by heating the green part under a continuous flow of nitrogen gas (flowing nitrogen gas, abstract) (page 235 Experimental Procedure section, page 239 Results and Discussion section). Myers teaches that sintering aluminum material with a sintering aid causes reaction-assisted liquid-phase sintering (page 233 Background section). Myers teaches that the sintered aluminum part has nearly full density (Table III, page 236 Results and Discussion section, page 241 Summary).
Both Liu and Myers teach similar processes for producing sintered 6061 alloy parts comprising a sintering aid.
In order to perform the embodiment comprising a densification (sintering) aid disclosed by Liu, applied above, it would have been necessary for one of ordinary skill in the art, at the time of filing, to supply the densification powder particles in some proportion. Considering Liu explicitly cites Myers for sintering with a sintering aid (column 1 line 64 to column 2 line 11) in determining sintering aid parameters for the process disclosed by Liu, it would have been obvious for one of ordinary skill in the art at the time of filing to select sintering aid proportions of 2-3% which Myers teaches as effective for sintering aids for 6061 aluminum alloys (Tables I-II, page 238 Results and Discussion section), thereby predictably proportioning feed material in the process disclosed by Liu in amounts suitable for liquid phase sintering taught by both Liu (column 7 lines 15-38) and Myers (page 233).
Liu discloses that the green article has about 10% by volume binder (column 6 lines 46-50). Liu does not teach weight percentages of the binder, and Liu does not teach results of varying binder amounts. Liu further does not exemplify embodiments comprising binder. Myers teaches embodiments wherein green article comprises 2% by weight and embodiments wherein the green article comprises 4% by weight (page 235 Experimental Procedure Section, pages 238-239 Results and Discussion section, Tables III, V). Myers teaches that the amount of binder in the manufactured part affects the performance of the part (page 238). Considering Liu does not disclose results, reasons, or specific examples for setting a binder to the disclosed volume fraction, whereas Myers teaches and exemplifies specific binder proportions and teaches that the binder proportions affect results (page 238), in order to ensure effective performance of the formed part, it would have been obvious to one of ordinary skill in the art at the time of filing to form the green part with 2% or 4% by weight binder, which Myers teaches as effective for producing such sintered aluminum parts (pages 235-236, 238), and which Myers teaches affects the performance of the formed part (page 238), thereby predictably forming a part with desired density and mechanical properties (pages 236, 238-239, Tables III, IV). 2% and 4% by weight are both within the claimed range of less than 5% by weight binder.
Liu discloses that where a binder has been used in forming the aluminum powder into a shape, the heating cycle is controlled to permit the binder to be removed (column 7 lines 31-33), and Myers teaches that gas flow can affect part distortion (page 241 Summary section). Liu in view of Myers does not disclose that the heating the green part (printed article) under nitrogen gas, applied above, comprises heating the green part under a continuous flow of nitrogen gas of at least 20 standard cubic feet per hour (SCFH).
Xiao teaches a method for producing a densified part (claim 1, [0001], [0019]). Xiao teaches forming a green part (billet) from build powder and a binder [0012], [0043], [0068]. Xiao teaches that the build powder comprises an alloy powder comprising alloy particles (stainless steel powder, as opposed to particles of constituent elements) [0044]. Xiao teaches densifying the green part by heating the green part under a continuous flow of nitrogen gas [0015-17], [0023-25], [0049-59]. Xiao teaches supplying the nitrogen flow at rates of 20L/min to 45L/min at stages of the sintering [0052-53]. Xiao teaches that the flow of nitrogen maintains the nitrogen equilibrium allowing nitrogen to enter pores [0052-53], which Xiao teaches allows more densely sintering as sintering temperature rises [0054]. Xiao further teaches heating for binder removal under a flow of nitrogen gas of 10-100 L/min (claim 6, [0025]).
Both Xiao and Liu in view of Myers, applied above teach producing a part by forming a green part from build material comprising binder and alloy powder particles and sintering under nitrogen gas.
It would have been obvious for one of ordinary skill in the art at the time of filing to provide the nitrogen in the method disclosed by Liu in view of Myers, applied above, at a continuous flow rate of 20-45 L/min because Xiao teaches that providing nitrogen in a sintering step at 20-45 L/min allows more densely sintering as sintering temperature rises [0054]. Further, considering Xiao teaches that a nitrogen flow of 10-100 L/min as suitable conditions for binder removal (claim 6, [0025]), a range of 20-45 L/min would predictably facilitate residual binder removal, which Liu discloses controlling in the heating step (column 7 lines 31-33). 20-45 L/min is equivalent to 42.4-95.3 cubic feet per hour, which meets a range of at least 20 SCFH.
Both Liu (column 5 lines 49-55) and Myers (page 233) teach controlling overall system particle size. While the Sn particle size taught by Myers (Table I) is sufficiently smaller than the 6061 alloy particle size taught by Myers (Table I) that the Sn particles likely would reside within spaces between alloy particles, Liu in view of Myers and Xiao does not teach specifically reasons for selecting relative particle sizes.
Hirata teaches an inkjet method for forming a part [0008], [0041-0042]. Hirata teaches forming a green part (three-dimensional shaped article) from build powder (first and second inorganic particles) and a binder (binding agent) [0008], [0009], [0020], [0025], [0041-42], [0046], [0118]. Hirata teaches that the build material comprises a first inorganic material which may be particles of an aluminum alloy powder [0045-46], [0053]. Hirata teaches that build material includes second inorganic material which may be a powder of copper, tin, lead, or silver [0008-10], [0086-88]. Hirata teaches densifying the green part by heating to sinter the part [0020], [0083], [0098]. Hirata teaches that ratio between the average particle size of the first inorganic particles and the average particle size of the second inorganic particles is in a range of 50000:1 to 10:1 [0089]. Hirata teaches that in sizing according to such a range of ratios, it is possible to allow the second inorganic particles to easily enter interstitial spaces (a void) between the first inorganic particles [0089], which renders possible an increase in density of both the first and second inorganic particles in a more uniform manner [0089], which yields a three-dimensional shaped article in which the density of the inorganic particles is increased in a more uniform manner [0089].
Both Hirata and Liu in view of Myers and Xiao teach methods for producing a densified part from a build material comprising inorganic particles and a binder.
It would have been obvious for one of ordinary skill in the art to size the densification (sintering) aid in the process disclosed by Liu in view of Myers and Xiao, applied above, such that the densification (sintering) aid resides in interstitial spaces of the aluminum alloy powder because Hirata teaches that sizing second organic particles to reside in interstitial spaces of first inorganic particles, results in an increase in density and an improved density uniformity [0089], thereby further facilitating density control in the process disclosed by Liu (column 8 lines 20-32). Densification aid residing in interstitial spaces of the aluminum alloy powder meets the sizing limitations of both claim 17 and claim 21.
Regarding claim 18, Liu discloses that the densified aluminum part (sintered article) has a relative density of at least about 60%; more preferably, a relative density of at least about 75%; even more preferably, a relative density of at least about 85%; and most preferably a relative density of at least about 95% (column 6 lines 30-35). Liu discloses that the parameters can be adjusted to arrive at a desired relative density (column 6 lines 23-30). The ranges of relative densities disclosed by Liu (column 6 lines 30-35) overlap a range of at least 97%. When claimed ranges overlap or lie inside ranges disclosed by the prior art a prima facie case of obviousness exists. See MPEP 2144.05(I).
Regarding claims 19, Liu discloses tin (Sn) as a densification (sintering) aid (column 6 lines 6-11, claim 7), and the densification (sintering) aid proportion taught by Myers, applied above, comprises tin (Sn) in 1% of the build powder (Table II). Note that claim 17 does not exclude additional material, such as a second densification (sintering) aid, such as magnesium from the build powder.
Regarding claim 20, Liu discloses that the aluminum alloy powder has a particle size in the range from about 1 micron to about 500 microns, and preferably a range from about 45 microns to about 106 microns (column 5 lines 49-55). Liu discloses reasons for why particles which are too coarse or too fine should not be used (column 5 lines 49-55). A range of about 1 micron to about 500 microns encompasses the range recited in claim 20, and a range from about 45 microns to about 106 microns overlaps the range recited in claim 20. When claimed ranges overlap or lie inside ranges disclosed by the prior art a prima facie case of obviousness exists. See MPEP 2144.05(I).
Conclusion
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/SEAN P. O'KEEFE/ Examiner, Art Unit 1738
/SALLY A MERKLING/ SPE, Art Unit 1738